Fast charging of batteries is now becoming well known. Reference will be made, hereafter, to several patents which are commonly owned herewith, and which teach various aspects of fast battery charging. Electric vehicles are now becoming more popular for a variety of reasons. Indeed, electric vehicles may become mandated to a greater or lesser extent due to the imposition of regulations requiring that at least a certain percentage of vehicles sold by any one manufacturer of vehicles--especially, passenger cars with seating from two to nine passengers, including the driver--and which are conventionally powered by internal combustion engines, must also include a specific number of vehicles that are so-called "zero emission" vehicles. That means that such vehicles have no emissions of noxious gasses, and the most common type of vehicle which would meet such stringent standards is an electric vehicle. Electric vehicles are powered by batteries, and present a number of problems or other difficulties to be overcome.
Not the least among those problems is the fact that in order for an electric vehicle to have any reasonable range--the distance that it can be driven--there has to be significant energy storage by way of batteries on board the vehicle. As the vehicle is driven, it uses energy delivered from the batteries, converting it to driving power delivered to the wheels of the vehicle, and thus there is only a finite distance or period of time over which the vehicle can be operated without requiring that the batteries be recharged.
Other related conditions also arise in respect of fleets of vehicles that are privately or corporately owned, but which may have differing purposes. For example, large manufacturing plants, distribution warehouses, and the like, may have a very considerable number of battery powered fork lift trucks, other traction or towing devices, and so on. Golf courses usually have a large number of golf carts to be rented by golfers playing a round of golf--indeed, some courses require that the players utilize a golf cart. Other such fleets may be localized, such as mail or courier package delivery carts that operate in a localized delivery route, day after day. All of those kinds of electric vehicles are also considered as candidates for becoming clients of charging stations in keeping with the present invention.
In another aspect of the invention, commercially operated "service stations" are contemplated. Thus, as the use of electric vehicles becomes more widespread, and such vehicles are essentially otherwise indistinguishable from ordinary passenger cars travelling on the roads, those cars may be driven further from home, or they may be rental vehicles used by visitors to a particular locale. In any event, there will be a growing requirement for such vehicles simply to pull into a station in much the same sense as an ordinary car would be driven into a service station for refuelling. In the case of an electric vehicle, however, instead of gasoline being placed into the fuel tank of the car, electrical energy is transferred into the batteries of the vehicle.
From the above, it is evident that there will exist a requirement for a significant number of charging stations to be available, as well as the requirement that each charging station should be capable of transferring electrical energy to the battery of the car as quickly as possible. Drivers of electric vehicles may be quite content to wait for 10 or 20 minutes for delivery of a significant amount of electrical energy (say, 20 kWh to 50 kWh); but they will not be willing to wait a number of hours for their electric vehicle to be recharged.
However, there is also increasing awareness of the fact that, by transmitting charging energy using high frequency alternating current, it is possible to reduce the size of the energy transfer components, and the size of wiring, and to take advantage of components and technology that are well advanced in respect of alternating current energy transfer. Still further, by arranging delivery of battery charging energy through a primary side of an inductive coupled transformer mounted at the interface between the charging station and the electric vehicle, it is possible to utilize high voltage, low current energy on the primary side with lower voltage, higher current energy on the secondary side of the inductive coupled transformer or inductive coupler. To accommodate these arrangements, however, there must be a slot or other receptacle on the vehicle, in which the secondary side of the transformer is to be found, while the primary side of the transformer will be found on a probe or plug which is inserted into the slot or receptacle of the vehicle so as to conclude the inductive coupling arrangement.
One particular advantage of such an arrangement is that the voltage and frequency conditions on the primary or charging station side of the inductive coupling interface may be set to be constant for all charging stations, no matter what may be the current acceptance characteristics and terminal voltage of the traction battery that is mounted in the vehicle. Thus, the voltage and current requirements for any specific traction battery in a vehicle are automatically accommodated by the specific design of the secondary side of the transformer which is mounted in the vehicle. Therefore, the vehicle or secondary side of the inductive coupler is thus battery and vehicle specific, for each vehicle and the traction battery mounted therein.
This, in turn, assures that the owner/operator of the vehicle may have full expectation of being able to recharge his traction battery, no matter at which charging station he is located; provided, of course, that there is a standardized physical requirement for the vehicle mounted receptacle and for the charging station energy transfer plug which form the secondary and primary sides, respectively, of the inductive coupled transformer.
The present invention demonstrates the awareness that there must be safe and efficient recharging in very short time periods; and, of course, in order for a charging station to deliver 20 to 50 kWh to an electric vehicle battery in 10 or 20 minutes, then the station must have high power ratings in the order of 100 to 300 kW. Such charging stations or battery chargers are not likely to be widely distributed so as to be found in everyone's garage. Moreover, such high power connections to the locally available power distribution grid are likely to be approved and located in more widely spaced distributions, perhaps not significantly different than the manner in which gasoline refuelling service stations are presently distributed, or even into strategic locations such as downtown public parking lots, and the like.
This, however, gives rise to yet another problem which is manifest with respect to electric vehicles, and will continue to be so. That is that electric vehicles such as automobiles and delivery vans, and the like, may have vastly different battery capacities, battery voltages, and perhaps even battery types.
Thus, as noted above, the present invention will overcome such difficulties by providing a universal charging station which has the capability of charging a large variety of electric automobiles and electric vehicles over a wide range of parameters--including, especially, initial charging current and initial voltage conditions under which the charging operation will take place.
Moreover, as noted above, it is self-evident that there must be an appropriate and compatible power connector or receptacle in order for the vehicle to be connected to a charging station in keeping with the present invention. Thus, the power connector by which an electric vehicle is connected to a charging station must, therefore, have at least two wires that are capable of carrying the maximum value of charging current to be delivered, at the delivery voltage. Moreover, as will be discussed in greater detail hereafter, there must also be communication means that are capable of transferring data concerning the state of charge of the battery being charged between the battery and the charging station.
It is, of course, taken for granted that any battery to be charged must be capable of accepting an initial charging current at a rate greater than 1 C--that is, at a rate in amperes that is greater than the capacity in ampere-hours of the battery.
It is anticipated that, in the future, most electric vehicles will be equipped with a Battery Energy Management System (BEMS). Such a system may be programmed so as to utilize charging algorithms which have been developed and are now becoming available to the market in association with the trade mark MINIT-CHARGER of Norvik Technologies Inc., the Assignee herein. Of course, other algorithms, or other battery charge controllers can be utilized, as discussed hereafter.
The present invention provides for a universal charging station which is capable of charging a great variety of electric vehicles, whether or not they have on board a sophisticated Battery Energy Management System controller, or other controllers, or even if they have no on board controller at all. Accordingly, a universal station in keeping with the present invention will, itself, be equipped with a power section--whose sole function is to deliver charging energy to the battery--and a charge control module whose purposes are described hereafter. The modes in which the universal charging station of the present invention may operate are, in descending order of their sophistication, as follows:
First, the charging station may function as a controlled current source under the control of a battery specific charging control module that is on board the electric vehicle. In that case, the controller section of the charging station acts as a slave to the on board battery specific charging control module in the electric vehicle, in a classical master-slave configuration.
Next, the charging station of the present invention may function substantially in keeping with MINIT-CHARGER technology, whereby the parameter of maximum initial charging current may be more or less automatically established by polling the electric vehicle to determine if there is on board a module which at least identifies the maximum charging current to which the battery should be initially subjected.
Finally, in a lesser degree of sophistication, the universal charging station of the present invention may operate in a mode by which the parameter of maximum initial charging current has been entered either manually or through a data interface by insertion of a card on which such data may be encoded.
Of course, these criteria are determined and discussed on the basis of energy transfer using an inductive coupled transformer. Thus, maximum initial charging current, or control of the charging current, are predicated on the characteristics of the transformer--and especially the secondary side thereof, since the primary side of the transformer is consistent at all charging stations--direct current charging energy that is delivered to the traction battery being charged is generally a high current, low voltage energy; notwithstanding that low current, high voltage energy has been delivered to the primary side of the inductive coupled transformer. Typically, the secondary side of the inductive coupled transformer is arranged to deliver nominal charging voltage in the range of 72 to 324 volts, as determined by the specifications of the battery to be charged. The primary side voltage will be in the range of 800 volts, but industry standards may eventually be settled in the range of less than 600 volts and perhaps as much as 1,200 volts, or more. In any event, current control is effected by controlling the value of current on the delivery or primary side.
In the first instance, the on board battery specific charging control module which is present in the electric vehicle makes the decisions, and sends signals to the charging station as to the magnitude and the timing of the charging current. In the latter two instances, control of the charging function is exercised by the charge control module located in the charging station.
There is, therefore, the provision made by the present invention that charging stations in keeping with the guidelines established hereby will offer enhanced "user friendliness" through its features. Those features may, for example, include a credit or debit card interface, whereby a retail customer may simply and easily pay for the energy delivered to his electric vehicle battery. The charging station may include registers whereby the initial charging current may be manually entered; or it may include a data interface whereby a card that is encoded with the charging parameters settings required for the specific battery carried in the electric vehicle may be inserted into the data interface to ensure that no mistakes or operator errors occur. That card may have the nominal charging voltage and maximum charging current data encoded into it such as by a magnetic stripe, or by such means as a memory chip, or by punched holes, or by embossed depressions and/or mounds, with the assumption that the data interface is compatible with any such card.
Still further, a charging station of the present invention might well be equipped with a meter which might define in advance the amount of energy to be delivered to the battery, or the monetary price of the energy to be delivered to the battery, together with appropriate shut off means to terminate the delivery of charging current when a predetermined amount of energy has been delivered or a predetermined monetary price of the energy has been delivered, whichever occurs first. Even further, the unit monetary price of the energy could be varied by controllers within the charging station, whereby the unit price for energy to be delivered from it may be dependent upon the time of day--it generally being understood that delivery of charging energy during ordinary daytime hours when demand for delivery of electrical energy from the local power authority is quite high, would mean that the unit price for the energy might be higher than in the evening when many offices, stores, and factories, etc., have shut down for the day. Indeed, as discussed hereafter, the local power authority may require a utility interface to be placed in the charging station, whereby it may communicate therewith over its own power lines to set and reset the unit valley price.
There may also be other load management and other functions such as facilities to bill the cost for charging energy delivered to an electric vehicle to the vehicle operator's office, interlock provisions to prevent theft of charging energy except with appropriate authorization to operate the charging station, and so on.
Thus, when the concept of the charging station is extended to a service station, there may be a number of similar charging stations or "charge dispensers" that are physically separated one from the other so that a plurality of electric vehicles can be accommodated. As discussed hereafter, a plurality of electric vehicles might be placed before a plurality of charging stations, all of which are conveniently connected to and fed by a single station rectifier. In any event, depending on the conditions, the multiple charging stations may be operated sequentially so as to charge one electric vehicle at a time, or several may be operated simultaneously provided that the amount of charging energy delivered at any one time does not exceed a predetermined maximum. In either event, priorities or other function controls may be imposed to ensure efficient utilization of the multiple charging stations connected to a common rectifier source. Of course, it also follows that local energy storage devices such as a flywheel unit or stand-by batteries might be provided for load levelling and so as to limit the peak power being drawn from the distribution power grid supplied by the local power authority.
It will also be understood that the operating functions of charging stations generally in keeping with the present invention will depend, at least in part, on the ability of the power section in the charging stations to turn on and turn off very quickly. Moreover, there may be provided a monitoring system which monitors the data communication link between the electric battery being charged and the power station, and the charge control modules may be established in such a manner that they continuously monitor and exchange signals periodically--say, every 0.5 to 2 seconds. The monitoring system would determine if there has been no communication of data over the communication link for a predetermined period of time--say, 4 to 6 seconds--and if so, signals would be initiated to shut down the charging operation so as to avoid serious implications of over-charge to the battery.
It is understood, of course, that the provision of charging energy to the primary side of the inductive coupler, at a frequency of from 10 kHz up to 200 kHz, would require that the charging station be equipped with an appropriately designed and dimensioned switching inverter module which is arranged to delivery energy at the selected primary voltage, and at the selected frequency. Each vehicle would, in turn, be equipped with the appropriately designed and dimensioned inductive coupler and a rectifier so as to deliver charging energy at the voltage level and charging current rates as are determined to be appropriate for the respective traction battery mounted in the vehicle.